Motion picture projector system

Abstract

A projector for motion picture film includes a servo motor which is controlled to advance film frame by frame to a projection station. A capstan on each side of the projection station is controlled to maintain film loops of substantially constant size and an associated reel motor delivers film to and takes film from each capstan. Each associated capstan and reel motor are controlled so as to maintain substantially constant tension on the film. A film guide defines the projection station and also includes provision for masking peripheral areas of each frame. Each capstan and an associated pinch roller are designed so as to eliminate creeping of film from between the two. A circuit for controlling the reel motors is arranged to permit fast winding of film directly from one reel to the other with an automatic braking feature.

What is claimed is: 
     
       1. A projector for motion picture film comprising means defining a frame aperture, means for projecting a beam of light through said aperture, a shutter for interrupting said light beam, a servo motor and means for connecting said servo motor to a strip of film, a circuit associated with said shutter for controlling said servo motor to cause it to position a frame of said film strip in said aperture during said interruption of said light beam, a capstan and a pinch roller on each side of said frame aperture, means for determining the amount of film between each of said capstans and said frame aperture, circuit means operatively connected to said amount of film determining means for controlling said capstans to maintain a film loop substantially constant size between each of said capstans an said frame aperture, a motor driven reel adjacent each of said capstans for storing film, and circuit means responsive to said capstan control circuit means for controlling each of said reels to take film from and supply film to corresonding ones of said capstans while maintaining substantially constant tension on said film. 
     
     
       2. A projector as claimed in claim 1 wherein said means for projecting a beam of light through said aperture includes a lamp, a mirror and a lens, each having dichroic surfaces to prevent transmission of infra-red light along the optical path. 
     
     
       3. A projector as claimed in claim 1 further comprising a housing, and a gate assembly on said housing between said reels and said shutter, said gate assembly including means for positioning each frame of said film in sequence before said shutter, said gate assembly being readily removable from said housing. 
     
     
       4. A projector as claimed in claim 1 wherein said means defining a frame aperture includes a guide body defining a substantially flat passage for said strip of film, said body having said aperture for projection of said beam of light through a frame of said film, a frame masking member slidable in said guide body and having a plurality of masking apertures therein for masking a frame of film, and means for sliding said masking member in said guide body to position a selected one of said masking apertures in said frame aperture. 
     
     
       5. A projector as claimed in claim 1 wherein said capstan and said pinch roller each have a cylindrical body with a frustoconical portion adjacent each end, said frustoconical portions on said pinch roller being mutually inverted with respect to those on said capstan and having the same slope as those on said capstan, whereby said frustoconical portions at corresponding ends of said capstan and said pinch roller are parallel and adapted to retain film therebetween. 
     
     
       6. A projector as claimed in claim 5 wherein said frustoconical portions on said capstan decrease in diameter toward the center of said capstan body while said frustoconical portions on said pinch roller increase in diameter toward the center of said pinch roller body. 
     
     
       7. A projector as claimed in claim 5 wherein said frustoconical portions slope at an angle of 2° with respect to the longitudinal axes of said capstan and said pinch roller. 
     
     
       8. A projector as claimed in claim 5 wherein the lengths of said capstan and said pinch roller are slightly less than the width of film to be held therebetween, whereby said film is bowed between said capstan and pinch roller. 
     
     
       9. Apparatus for advancing a frame of a motion picture film during the closed position of a shutter comprising, a servo motor, means connecting said servo motor to said film, means for generating a signal indicating a closing of said shutter, switch means for providing a selected frame rate command, means for providing signals in response to successive predetermined angular positions of the servo motor shaft, circuit means responsive to said shutter-closed signal and said frame rate command and said angular position responsive signals in sequence for producing acceleration, constant velocity and deceleration signals in sequence and, means responsive to said acceleration, constant velocity and deceleration signals for controlling said servo motor to advance said frame. 
     
     
       10. Apparatus as claimed in claim 9 wherein said means for generating a signal indicating a closing of said shutter includes means for providing a light beam and means for providing a pulse in response to interruption of the light beam by said shutter, and further comprising a divider for dividing the rate of said light interruption responsive pulses to produce a plurality of pulse trains having different pulse rates, each pulse in each pulse train indicating a closing of said shutter, and circuit means for selecting one of said pulse trains in accordance with said selected frame rate command. 
     
     
       11. Apparatus as claimed in claim 9 further comprising means for providing a selected direction command signal and wherein said acceleration, constant velocity and deceleration signal responsive means is also responsive to said selected direction command signal for controlling said servo motor to advance said frame in the desired direction. 
     
     
       12. Apparatus as claimed in claim 9 wherein said means for providing signals in response to successive predetermined angular positions of said servo motor includes a slotted disc mounted on the shaft of said servo motor, a light source and a light sensor mounted on opposite sides of said disc for producing signals that vary in accordance with the variations in light passing said disc. 
     
     
       13. Apparatus as claimed in claim 12 further comprising an amplifier connected to the output of said light sensor, said amplifier providing a zero output signal when the light beam from said light source is centered at the edge of a slot, providing a maximum signal of one polarity when said light beam is centered at the center of a slot and providing a maximum signal of the opposite polarity when said light beam is centered at the center of a space between slots. 
     
     
       14. Apparatus as claimed in claim 13 wherein said slots are spaced at 30° intervals about the periphery of said disc, said acceleration signal occurs during 15° of angular rotation of said servo motor shaft, said constant velocity signal occurs during 30° of angular rotation at the end of said acceleration signal, and said deceleration signal occurs during 15° at the end of said constant velocity signal. 
     
     
       15. Apparatus as claimed in claim 13 wherein the output of said amplifier is provided to said servo motor to maintain and correct the position of said frame of film in the absence of a shutter-closed signal. 
     
     
       16. Apparatus as claimed in claim 9 wherein said means responsive to said acceleration, constant velocity and decleration signals comprises an analog switch controlled by said signals and an amplifier connected between said servo motor and said analog switch, input signal means for said amplifier connected to the input of said analog switch for providing input signals to said amplifier to cause it to drive said servo motor in accordance with said acceleration, constant velocity and deceleration signals. 
     
     
       17. In a motion picture projector having a projector station, the combination comprising a capstan and capstan motor for driving film, solid state switch means for supplying current to drive said capstan motor in either direction of rotation, means for determining and providing a signal indicating the amount of film stored between said capstan and said projection station, means responsive to said stored film signal for providing a signal to said solid state switch, means to drive said capstan motor in the proper direction to maintain a substantially constant amount of stored film, and a reel and reel motor for providing film to and receiving film from said capstan. 
     
     
       18. The combination as claimed in claim 17 further comprising, solid state switch means for supplying current to said reel motor in one direction and, control switch means connected between said capstan motor solid state switch means and said reel motor solid state switch means for causing said reel motor switch means to supply current to drive said reel motor in accordance with the amount and direction of current supplied to said capstan motor to maintain constant tension on said film. 
     
     
       19. The combination as claimed in claim 17 wherein said film stored between said capstan and said projection station is in the form of a loop and said means for determining and providing a signal indicating the size of said loop comprises a light source and a light sensor for sensing the amount of light reflected from said film loop and providing a signal indicating said amount. 
     
     
       20. The combination as claimed in claim 17 wherein said means responsive to said stored film signal comprises an operational amplifier having a dual polarity output signal. 
     
     
       21. The combination as claimed in claim 18 wherein said capstan motor solid state switch means includes a transistor for supplying current to said capstan motor to cause it to drive film toward said loop, and wherein said control switch means comprises a transistor having its base and emitter connected across an emitter resistor of said capstan motor transistor and having its collector connected to said reel motor switch means to cause said reel motor switch means to increase current to said reel motor as current through said capstan motor transistor decreases, and to decrease current to said reel motor as current through said capstan motor transistor increases, whereby substantially constant tension is maintained on said film. 
     
     
       22. In a motion picture projector having a pay-out reel motor and a take-up reel motor, a circuit for controlling said reel motors for fast winding of film from said pay-out to said take-up reel comprising, a solid state switch means for each reel motor for supplying current thereto, a control switch coupled to each solid state switch means, logic switching means having respective outputs connected to said control switches, respectively, for providing fast wind signals to cause current to be supplied to said take-up reel motor for fast winding of film, and means between said solid state switching means for said take-up reel and said logic switching means for providing a logic signal to said logic switching means indicating the conductive state of said solid state switching means, said logic switching means being arranged to provide a signal to said control switch of said pay-out reel motor to cause current to be supplied to said motor when said take-up reel solid state switch is conductive and said fast wind signal to said take-up reel control switch is removed, whereby said current to said pay-out reel motor brakes said pay-out and take-up reels. 
     
     
       23. A circuit as claimed in claim 22 wherein said means for indicating the conductive state of said take-up reel solid state switching means includes a delay means, whereby braking current to said pay-out reel is interrupted after a delay. 
     
     
       24. A projector as claimed in claim 1 further comprising switch means for selecting a frame projection rate, said switch means operatively connected to said circuit for controlling said servo motor to cause it to position a frame of film in said aperature during certain interruptions of said light beam in accordance with said selected frame projection rate. 
     
     
       25. Apparatus for projecting motion picture film at variable rates of speed comprising means defining a frame aperature, means for projecting a beam of light through said aperature, a shutter for interrupting said light beam by successively closing and opening at a substantially fixed rate, means for generating a signal indicating a closing of said shutter, a servo motor and means for connecting said servo motor to a strip of film, switch means for selecting a frame projection rate, means operatively connected to said switch means and to said shutter-closed signal generating means for producing a command signal to advance a frame during the closed position of said shutter in accordance with the selected frame projection rate, circuit means responsive to said command signal producing means for controlling said servo motor to cause it to position a frame of said film in said aperature. 
     
     
       26. Apparatus as claimed in claim 25 further comprising a capstan on each side of said frame aperature, circuit means for controlling said capstans to maintain a substantially constant amount of film between said capstan and said frame aperature, a motor driven reel adjacent to each of said capstans for storing film, and circuit means for controlling each of said reels to take film from and supply film to corresponding ones of said capstans.